1. Field of the Invention
The present invention generally relates to high speed data communications wherein signal information is processed both in digital and analog forms. More specifically, the invention relates to a system and method that uses a single digital subscriber line (DSL) transmission unit within an end office of the public switched telephone network (PSTN) to establish high speed communication links with multiple users in a multi-drop network.
2. Discussion of the Related Art
In recent years, telephone communication systems have expanded from traditional plain old telephone system (POTS) communications to include high-speed data communications as well. As is known, POTS communications include the transmission of voice information, control signals, public switched telephone network (PSTN) information, as well as, information from ancillary equipment in analog form (i.e. computer modems and facsimile machines) that is transmitted in the POTS bandwidth.
Prompted largely by the desire of large businesses to reliably transfer information over a broadband network, telecommunications service providers have employed digital subscriber lines (DSL) to provide a plethora of interactive multi-media digital signals over the same existing POTS twisted-pair lines. The provision of DSL services to customer premise has proliferated over recent years as the small office, home office (SOHO) market desires to take advantage of the increased bandwidth and data transfer rates provided by DSL. DSL services are typically provided to remotely located customer premise by equipping both the appropriate central office and the customer premise with compatible DSL modems.
DSL modems communicate by modulating a baseband signal with customer desired service signals, converting the modulated digital data signal to an analog signal, and transmitting the analog signal over the conventional copper wire pair provided in the PSTN from a central office to a customer premise via a carrier service area (CSA) loop. Well known data modulation and transmission techniques include mapping digital data to be transmitted into a multi-dimensional multi-level signal space constellation and decoding the received constellation to recover the transmitted information.
As various DSL standards evolved, it became clear that it would be highly desirable to deliver a high-speed DSL service that is as easy to operate and use as a dial-up modem, thus leading to the concept of DSL-Lite. DSL-Lite or G.Lite includes provisions for connecting a DSL line without the need for splitters at the customer premise equipment-end (CPE) of the network. During standards development, it was observed that there are over 15 million households in the United States that have two or more PCs. As a result, equipment manufacturers began to address the SOHO networking market by introducing a variety of traditional products including routers, bridges, etc., which required additional premise wiring and user expertise in network configuration, maintenance, and troubleshooting.
On a local area network (LAN), a media access control (MAC) or address is required to properly direct information to each of the individual computers or nodes on the LAN. On a LAN, a MAC address is a computer's unique address and may be in a “hard-wired” form. On an Ethernet LAN, it is the same as the computer's Ethernet address. When connected to the Internet, a connection table maps the Internet protocol (IP) address to each computer's physical address on the LAN. As currently defined, DSL standards do not provide a MAC capable of operating in a multi-point environment as there are no MAC addresses in DSL.
Another way of stating the problem is that in the downstream direction, the central office (CO) digital subscriber line access multiplexer (DSLAM) has no mechanism for differentiating between two or more network devices in a multi-drop environment, as DSL does not provide for auto-configuration of multiple IP addresses in a multi-point configuration. Similarly, in the upstream direction, there is no way for multiple devices to gain access to the upstream channel. As a direct result, DSL applications have been limited to operating as point-to-point communications links.